The present invention relates to intermodal trains for transport of semi-trailers and, more particularly, to a combination ramp and rail car for allowing semi-trailers to be driven onto such trains and for transporting a semi-trailer.
It has become common practice to transport semi-trailers by rail cars and special rail cars have been developed specifically for such purpose. These special cars are generally known as articulated flat cars and are designed to be coupled together in intermodal trains such that a semi-trailer can be driven over the cars from one end of the train to another end in a practice commonly referred to as circus style loading/unloading. Flat cars other than articulated cars are also used in circus style loading/unloading, using ramps extending between adjacent cars.
A general problem with loading/unloading semi-trailers on rail cars is how to raise/lower the trailers between ground level and the rail car bed. In some instances, loading is restricted to special loading platforms. At some locations, semi-trailers are lifted by overhead crane. Both these solutions are limiting since loading/unloading is restricted to those areas having such special facilities.
One method of loading semi-trailers on rail cars, as shown in U.S. Pat. No. 5,222,443, employs a ramp car constructed of two separable ramps extending toward each other and adapted to be locked together in a raised travel position. Opposite ends of the ramps are mounted to respective wheel sets such that the joined ramps are supported on the wheel sets for travel. The overall assembly is complex, requiring power and control means for assembling/disassembling the ramps. Furthermore, the assembled ramp car occupies space in the train and is unusable for any other purpose. Open space in a train increases wind drag and reduces fuel economy.